kevc66
Hello,
I installed a 20kw with LTS. The home has a geo thermal unit with 10kw electric backup heat. I would like to have backup heat only active when powering the home with the generator. I am going to use a contactor to disconnect the main heat source. My questions.

1. What is the best way to shut down the geo thermal. Control power or control low voltage control wiring?

2. If controlling the control wiring, Which wires would need to be controlled in the electrical enclosure at the geo unit?

3. Would it be better to use a normally open or a normally closed contactor?

4. Where would be the best place in the LTS to tap off 120V for the contactor coil?

5. Lastly, will Generac be offering any optional load control similar to what is in the Nexus Smart switch.

Thanks for taking the time to answer!
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yucan2
kevc66;7989 wrote:
Hello,
I installed a 20kw with LTS. The home has a geo thermal unit with 10kw electric backup heat. I would like to have backup heat only active when powering the home with the generator. I am going to use a contactor to disconnect the main heat source. My questions.

1. What is the best way to shut down the geo thermal. Control power or control low voltage control wiring?

2. If controlling the control wiring, Which wires would need to be controlled in the electrical enclosure at the geo unit?

3. Would it be better to use a normally open or a normally closed contactor?

4. Where would be the best place in the LTS to tap off 120V for the contactor coil?

5. Lastly, will Generac be offering any optional load control similar to what is in the Nexus Smart switch.

Thanks for taking the time to answer!


I'm not following you at all. The LTS is a load shed switch. Are you not using it as such? It's very capable of doing what you describe.
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kevc66
reply

Hello,
Yes I am aware of the capablities of the load shed transfer switch. However, the geo thermal unit is too large of a load to run on the generator, along with the other circuits. The customer has gas fireplaces to provide most emergency heat, but would like to run his geo thermal system's backup auxillary heat (10kw resistive heat strip) to provide minimal heat elsewhere. Since the auxillary heat uses less power the main geo unit, he would rather have me power the auxillary heat strips. Therefore, what is the best way to deenergize the geo thermal pump circuit during utility loss. So that the system uses auxillary backup heat.Is it better to install a contactor to control line power or use a contactor to control the low voltage control wires of the system. If low voltage control, how (which control wires do you run through contactor).
The other question about the LTS switch is that you can use it to shed loads, but I would like to also be able to sequence heat pump compressor starts in homes with multiple systems. Just like the new Nexus switches. It would be nice if we were able to have the function of the LTS and the load sequencing controls all in one unit.

Thanks
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ohmslaw
Generac makes a very nice load shed module. They include it in all of the nexus switches. I bought a couple to install in the 8-10 kw load centers. I am planning on installing it in a box external of the load center. I would think you could use one for your application. I think Generac should sell them as a plug and play device for the load centers.
Tim
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yucan2
kevc66;7991 wrote:
Hello,
Yes I am aware of the capablities of the load shed transfer switch. However, the geo thermal unit is too large of a load to run on the generator, along with the other circuits. The customer has gas fireplaces to provide most emergency heat, but would like to run his geo thermal system's backup auxillary heat (10kw resistive heat strip) to provide minimal heat elsewhere. Since the auxillary heat uses less power the main geo unit, he would rather have me power the auxillary heat strips. Therefore, what is the best way to deenergize the geo thermal pump circuit during utility loss. So that the system uses auxillary backup heat.Is it better to install a contactor to control line power or use a contactor to control the low voltage control wires of the system. If low voltage control, how (which control wires do you run through contactor).
The other question about the LTS switch is that you can use it to shed loads, but I would like to also be able to sequence heat pump compressor starts in homes with multiple systems. Just like the new Nexus switches. It would be nice if we were able to have the function of the LTS and the load sequencing controls all in one unit.

Thanks


I'd parallel N1 and N2 sensing wires to a 240 volt coil that controls a 2 pole contactor, in separate enclosure of course.

In the event of a loss of power the contactor will prevent the load attached to it from running or as Tim said, you could use one of Generac's off the shelf load shed modules.
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Gman1
I'd find the thermostat wire that controls the strip heat and break it when the gen is running.
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ERDoc
I have a 20KW unit running two 4 ton geo units. I have my electric back-ups disabled while on generator power. I have never had a problem except once both tried to fire up at the same time. To get around this problem on is on primary the other is on the load shed side. I did have to put bigger capacitors in the geo units, but I find it hard to beleive that a single geo unit can ever draw more thank the 10KW electric strip.
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d11gnccer
Starting watts on the compressor will draw more than the 10kw resistance heat. Does this geothermal have two power feeds or just one? On larger electric furnaces, say 20kw, we have backed up one circuit that controls the transformer/blower/ with 1 or 2 heat banks. The other circuit feeding the other 2 heat banks is not on generator power.
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kevc66
Hello,
Thanks for the replies. The problem with the geo thermal unit is the compressor starting. It is bogging down the generator to the point of almost stalling the unit. The customer insists on having heat on all the time. Theerfore, I powering the steady known load. The 10kw heat coil. I would like to see load sequencing in the LTS unit. At least as an addon feature.
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